It took us almost two months to comb through dad's house, sorting the myriad pieces of his unpursued passions into several appropriate piles for disposal.

• Keep.
• Sell.
• Donate.
• Trash.

He didn't have much in the way of food, but cookbooks in mint condition spilled out of his kitchen cupboards. Mystery novels were stacked neatly on his bedside table, suffocating under layers of dust. Princess Di's biography and Stephen King's The Shining lay face down on the coffee table, spines cracked towards the ceiling. Poets hid, forgotten, behind the basement bar. Daunting masterpieces of Joyce, Hugo, and Dumas stood proper and pristine in the bookcases of his spare bedroom. Harry Potter, curiously, was lined up neatly on the workbench in his garage next to an impressive collection of equipment manuals. Donate.

While I examined every paternal artifact with the zeal of an amateur archaeologist, my sister, Kate, executed our job grudgingly, methodically, the corners of her mouth tugged down in mild distaste. She held no curiosity for the life that gave us life, and I assumed her interest in him extended only as far as his had in her.

We waded through a world of short-lived hobbies. The shed in the yard boarded gleaming gardening tools, unspoiled art supplies, and a pair of cross country skis still marked with a discount sticker. Sell.

We purged every nook and cranny in the house of unused useful treasures. Three hundred glass mason jars collected dust and spiders in the alcove under the stairs; forty-five rolls of scotch tape curled up on their sides, stacked haphazardly in the cupboard above the washing machine; three five-gallon pails of assorted nails, screws, and bolts rusted behind the furnace. Keep. Donate. Trash.

A Yamaha keyboard piano emerged from under piles of forgotten laundry. Sell. Beginner sheet music for the guitar we'd never heard him play was buried in a wicker basket under a cascading mountain of magazines. The guitar in question was wildly out of tune. I strummed a dissonant chord absentmindedly, prompting Kate to grab and drop it with a reverberating hum next to a harmonica, a violin bow, and an assortment of small percussion instruments. Donate.

"We could sell that!" I exclaimed.

"He bought it at Walmart," she replied flatly, and I briefly wondered how she knew.

Dad hadn't been a bad guy, as far as I remember. I recalled him doing all the right dad things "teaching me to throw and catch a ball, taking us to the county fair to eat too much candy, bringing home a wriggling bundle of floppy ears and sad eyes that we crossed our hearts to feed, train, and walk (naturally, and much to her disgruntled dismay, it became mom's exclusive responsibility)".

It was just that, between the checked boxes of fatherhood, absence was his only constant.

Early on, it was missed birthdays, disappointing Christmas mornings, and an empty seat in the stands at my B Division hockey games. By the time I was ten, he banged through our door only once or twice a year. Kate would quietly disappear to a friend's; mom would gravitate as if on auto-pilot into the kitchen to prepare a meal; I would hover, eager to brief him on my latest activities and accomplishments, hopeful he would finally divulge something about the band with which he was surely traveling, or the secret mission on which he must have been deployed. "This and that" was all he ever offered.

When Kate left home, he came around even less often.

I waded into the unmired moodiness of my teenage years and developed (feigned) indifference in his disinterest. By the time I crashed clumsily from adolescence to adulthood, dad was a sort of non-entity that flitted and fluttered at the edges. He attended my university convocation, but didn't stick around for the celebratory dinner. He stood by us at mom's funeral, appropriately sad, but left us to make the arrangements and deal with her estate. He was invited to Kate's wedding, but she asked me to walk her down the aisle.

At Kate's orders, I tackled the bedroom, while she disappeared for days under unreasonable hoards of wooden spoons, tacky coffee mugs, and canned goods. The stench of sickness still clung to his mattress and its clothes. Trash. The neglected novels on his bedside table were jacketed in dust and blanketed in crusty tissues. Trash. Drawers were mostly empty save for a rolling lip chap and a handful of loose change. The rest of the furniture appeared in fine health. Sell.

Rifling through his closet, I found only a few crumpled receipts in the pockets of his clothes. Donate. My climbing bewilderment and disappointment reached their peak. A lifetime of pretending not to care aside, we finally had unfettered access to the private life of our flighty father. I wanted to find a trunk of sentimental memories in his basement, or a shoe box of photographs labelled with hard-to-read names stuffed in the closet, or a stack of secret-littered journals on the bookshelves. But the modest 900 square-foot house rejected my foolish fantasies.

Last year, Kate had learned dad was unwell. "Oh, by the way," she hesitantly tacked on to our annual phone call, "Dad's been in the hospital."

I paused, caught off guard by her mention of his existence and, further, her awareness of his illness. I'd wanted to know more "what was wrong, should we go visit, who was taking care of him, who called her" but my tyrant nephews were wailing in the background, and she took advantage of my silent beat to skewer the conversation. "He's fine now, at home, I guess. Listen, don't worry about it" She trailed off as the cacophony of family anarchy rose with a mighty crescendo, and the line died.

I didn't call back, and neither did she. The next time we spoke, she delivered a dispassionate dispatch. "He's dead."

Now we stand among life's leftovers.

• Keep. Empty.
• Sell. Posted.
• Donate. Boxed.
• Trash. Bagged.

There is no heirloom-worthy jewelry. There are no old family photos. There aren't any accolades or love letters, not even a final will and testament. Nothing in seventy years' worth of accumulation sheds a shred of light on who dad was or why.

I watch my sister lug bags and boxes out the door, and wish there was someone left who knew him.

When the trucks are packed and the house echoes in vacant relief, we stand on the front porch and watch the realtor pound a For Sale sign into the frosty lawn. I mutter, "I should have gone to see him, you know, before&"

Kate turns and looks up at me with the most peculiar expression of incredulity. She puts her gloved hand on my arm. For a long quiet moment it feels like she's trying to convey something important, but all she leaves me with is: "See you at Christmas."

And then she's gone without looking back, bounding down the cracked concrete towards her car with a lightness in her step I've never seen before.

Credit: Christina Marie

We are made of stardust, the saying goes, and a pair of studies including University of Michigan research finds that may be more true than we previously thought.

The first study, led by U-M researcher Jie (Jackie) Li and published in Science Advances, finds that most of the carbon on Earth was likely delivered from the interstellar medium, the material that exists in space between stars in a galaxy. This likely happened well after the protoplanetary disk, the cloud of dust and gas that circled our young sun and contained the building blocks of the planets, formed and warmed up.

Carbon was also likely sequestered into solids within one million years of the sun's birth -- which means that carbon, the backbone of life on earth, survived an interstellar journey to our planet.

Previously, researchers thought carbon in the Earth came from molecules that were initially present in nebular gas, which then accreted into a rocky planet when the gases were cool enough for the molecules to precipitate. Li and her team, which includes U-M astronomer Edwin Bergin, Geoffrey Blake of the California Institute of Technology, Fred Ciesla of the University of Chicago and Marc Hirschmann of the University of Minnesota, point out in this study that the gas molecules that carry carbon wouldn't be available to build the Earth because once carbon vaporizes, it does not condense back into a solid.

"The condensation model has been widely used for decades. It assumes that during the formation of the sun, all of the planet's elements got vaporized, and as the disk cooled, some of these gases condensed and supplied chemical ingredients to solid bodies. But that doesn't work for carbon," said Li, a professor in the U-M Department of Earth and Environmental Sciences.

Much of carbon was delivered to the disk in the form of organic molecules. However, when carbon is vaporized, it produces much more volatile species that require very low temperatures to form solids. More importantly, carbon does not condense back again into an organic form. Because of this, Li and her team inferred most of Earth's carbon was likely inherited directly from the interstellar medium, avoiding vaporization entirely.

To better understand how Earth acquired its carbon, Li estimated the maximum amount of carbon Earth could contain. To do this, she compared how quickly a seismic wave travels through the core to the known sound velocities of the core. This told the researchers that carbon likely makes up less than half a percent of Earth's mass. Understanding the upper bounds of how much carbon the Earth might contain tells the researchers information about when the carbon might have been delivered here.

"We asked a different question: We asked how much carbon could you stuff in the Earth's core and still be consistent with all the constraints," Bergin said, professor and chair of the U-M Department of Astronomy. "There's uncertainty here. Let's embrace the uncertainty to ask what are the true upper bounds for how much carbon is very deep in the Earth, and that will tell us the true landscape we're within."

A planet's carbon must exist in the right proportion to support life as we know it. Too much carbon, and the Earth's atmosphere would be like Venus, trapping heat from the sun and maintaining a temperature of about 880 degrees Fahrenheit. Too little carbon, and Earth would resemble Mars: an inhospitable place unable to support water-based life, with temperatures around minus 60.

In a second study by the same group of authors, but led by Hirschmann of the University of Minnesota, the researchers looked at how carbon is processed when the small precursors of planets, known as planetesimals, retain carbon during their early formation. By examining the metallic cores of these bodies, now preserved as iron meteorites, they found that during this key step of planetary origin, much of the carbon must be lost as the planetesimals melt, form cores and lose gas. This upends previous thinking, Hirschmann says.

"Most models have the carbon and other life-essential materials such as water and nitrogen going from the nebula into primitive rocky bodies, and these are then delivered to growing planets such as Earth or Mars," said Hirschmann, professor of earth and environmental sciences. "But this skips a key step, in which the planetesimals lose much of their carbon before they accrete to the planets."

Hirschmann's study was recently published in Proceedings of the National Academy of Sciences.

"The planet needs carbon to regulate its climate and allow life to exist, but it's a very delicate thing," Bergin said. "You don't want to have too little, but you don't want to have too much."

Bergin says the two studies both describe two different aspects of carbon loss -- and suggest that carbon loss appears to be a central aspect in constructing the Earth as a habitable planet.

"Answering whether or not Earth-like planets exist elsewhere can only be achieved by working at the intersection of disciplines like astronomy and geochemistry," said Ciesla, a U. of C. professor of geophysical sciences. "While approaches and the specific questions that researchers work to answer differ across the fields, building a coherent story requires identifying topics of mutual interest and finding ways to bridge the intellectual gaps between them. Doing so is challenging, but the effort is both stimulating and rewarding." =

Blake, a co-author on both studies and a Caltech professor of cosmochemistry and planetary science, and of chemistry, says this kind of interdisciplinary work is critical.

"Over the history of our galaxy alone, rocky planets like the Earth or a bit larger have been assembled hundreds of millions of times around stars like the Sun," he said. "Can we extend this work to examine carbon loss in planetary systems more broadly? Such research will take a diverse community of scholars."

Funding sources for this collaborative research include the National Science Foundation, NASA's Exoplanets Research Program, NASA's Emerging Worlds Program and the NASA Astrobiology Program.

Copied From: Science Daily
Source: University of Michigan